Our goals concern the visual function of the two functional streams that may be identified in the monkey's geniculo-cortical visual pathway. Our working hypothesis is that these streams subserve different visual functions, and that different forms of developmental visual disorder may reflect abnormalities that are primarily confined to one or the other of these streams. 1. We will continue our quantitative studies of the functional properties of neurons in the striate cortex of the macaque. We will pay particular attention to the relay of spatial, temporal and chromatic information by different neural groups, and to the distribution of neurons with particular properties within the functional architecture of the cortex. 2. In order to study the functions of extrastriate visual areas, we will obtain an accurate quantitative description of the response properties of neurons in several areas of the macaque's extrastriate visual cortex. A particular concern will be to establish the stimulus dimensions for which neurons in a particular area show an invariant selectivity. The areas to be studied will include V2, V3, V3a, the V4 complex, and MT. Having identified candidate stimulus dimensions for at least some of these areas, we will use statistical methods to compare the performance of neurons with psychophysical measures of performance, using stimuli designed to tap particular kinds of visual capacity related to the dimensions for which invariants have been identified. In order to study the degree to which neural properties in each area are simply derived from their inputs, and the degree to which they result from significant local processing, we will identify and characterize the neurons in V1 and V2 that project to particular higher-order areas, and compare their properties with those of neurons in their target areas. 3. We will study the visual behavior of monkeys reared in ways that create conditions resembling human strabismic and anisometropic amblyopia. We will establish how experimental amblyopia affects spatial contrast detection and discrimination, chromatic constrast detection, and the visual space sense, in order to characterize the changes that occur in psychophysically-defined visual mechanisms. We will attempt to link particular functional deficits to clinically-identified visual problems. 4. We will study the way in which the development of the functional properties of neurons in striate and extrastriate visual cortex is affected by experimental amblyopia. We are particularly interested in establishing the relationship between the psychophysical and neural changes underlying the amblyopic deficit. Our working hypothesis is that anisometropic amblyopia primarily involves a deficit in the "parvocellular" stream, while strabismic amblyopia also involves important deficits in the "magnocellular" stream. Thus, the overall goals of this project are concerned with understanding the cortical mechanisms underlying normal visual performance, and the way in which those mechanisms are altered by amblyopia.